In Campaign mode you have get new types of unit to command on each
level. Every Campaign level has a Star challenge which unlocks a unit
for Freeplay mode. In Freeplay you can use all your unlocked units to
aim for high scores.

Controls

Mouse:
* Click Unit Buttons in Top Left to Select
* Click Windows to Place Units
* Click Units with a Gold Star to Upgrade (Costs Gold)
* Move Mouse to Bottom Left of screen to Speed Time